Detecting the onset and effects of major northern hemisphere glaciation in the abyssal tropical Atlantic Ocean
Other literature type
Hayek, Lee-Ann C.
(issn: 1814-9332, eissn: 1814-9332)
The cooling trend of the Neogene resulted in
diachronous development of glacial
conditions, southern high latitudes glaciating
This cooling culminated in the
early Pleistocene (2.54 Ma) onset of major glaciation,
during which large areas of high latitude
land and sea in both hemispheres were periodically blanketed with ice.
However, this onset
at low latitude abyssal depths
are elusive. This paper examines the abyssal benthic
ity in the Atlantic Ocean near the Northern Equatorial Countercurrent, in
ODP Hole 926A (Ceara Rise), off the River Amazon. Using
an assemblage turnover index
(ATI), a related conditioned-on-boundary index (CoBI) and SHE analysis, we
show how a
mean assemblage turnover coincides with the early Pleistocene onset of northern
hemisphere major glaciation.
The community comprises primarily phytodetritivores
(<i>Alabaminenella weddellensis</i>, <i>Epistominella exigua</i>
<i>Globocassidulina subglobosa</i>), the proportional abundances of which differ before and after 2.54 Ma.
Coupled with changes in the
abundances of <i>Nuttallides umbonifera</i>,
spp., alterations in the
abundances of the
after 2.54 Ma show that the
in biotic turnover at
depth resulted from enhanced organic carbon flux from sea surface water. This was probably related to forced southward repositioning of the inter-tropical convergence zone (ITCZ) by the
growth of the northern hemisphere ice caps.
This was coupled with an increase in bottom
current velocity, as shown by a change in the abundance of